Below, I’m can use tidyr::pivot_longer(DATA, -InstNm, names_sep = "_", names_to = c("Indicator", ".value")) to get very close to my Desired_output.

But I wonder how I can exactly achieve my Desired_output where CPct and EPct are merged as one column called CPct_EPct?

DATA <- read.table(header=T, text=
"InstNm    OTE_CPct OTE_L OTE_P    OTE_R      RAE_EPct RAE_NPct RAE_L RAE_B RAE_P  RAE_R
 Baker          60      1     1  Limited            56     76     1     0     1   Limited")

Desired_output <- read.table(header=T, text=
"InstNm    Indicator Rating   NPct  CPct_EPct  L   P  B
 Baker     OTE      Limited    NA        60    1   1  NA
 Baker     RAE      Limited    76        56    1   1  0")